In prior art testing of monopulse radar signal processing circuitry, use of the complete radar system to obtain complete angle-error information from complex reflective sources of energy required a large area for accurate testing. A signal was required to be transmitted to a far-field target for reflection back to the radar circuitry under test. Current state of the art methods employ a real-time computer controlled radar simulator utilizing an anechoic chamber designed for a specific range of rf frequencies. Thus a new chamber is required if the rf frequency band of interest does not lie within the specifications of the chamber. Use of an anechoic chamber also inherently restricts the application of the simulator to passive and semi-active sensors. A limited number of discrete signals must be radiated in such chambers to simulate continuous functions such as the spatial and frequency characteristics of radar clutter. In many radar systems the physical features may not be amenable to rf chamber simulation in that, for example, the antenna may have to operate within its near-field and system tracking accuracy may be desired which exceeds target positioning capabilities within the chamber, resulting in inaccurate results.
Monopulse radar systems are disclosed in the "Radar Handbook" by Skolnik published by McGraw-Hill Book Company in 1970, reference section 21.4 and page 21-13 for a block diagram of a conventional monopulse radar. In current systems for testing the limits of the radar signal processing circuitry, the monopulse feedhorn and antenna assembly are placed in an anechoic chamber for receiving rf signals from an antenna representing a target that reflects energy toward the receiver. Typically the target antenna has signals representing target signal strength, clutter, and electronic countermeasures signals incorporated therein. These signals are initiated by a master control computer which activates slave computer systems to initiate the signal generating equiment to electronic countermeasures equipment, or random noise equipment as desired to cover the span and intensity of signals which should be detected by the radar signal processing circuitry. Upon command from the master control computer the slave computers may generate digital control signals which are fed to appropriate signal generation hardware or random noise hardware to simulate random phenomenon such as amplitude scintillation, which is used in the calculation of the digital control signals. Signal generation equipment interface circuitry takes the digital control signals from the computers and provides the control signals to the signal generation equipment in the proper format which allows the rf antenna to simulate a target. Typical of these prior art computer systems is the model CDC6600 computer provided by Computer Development Corporation.